1. Field of the Invention
The present invention relates to providing tight seals along shafts by means of laser energy and more particularly to laser bonding of medical device shaft geometries.
2. Description of Related Art
Balloon catheters are well known for their utility in treating certain types of obstructions in blood vessels. In a Percutaneous Transluminal Coronary Angioplasty (PTCA or balloon angioplasty) procedure, catheters are inserted into the cardiovascular system. A pre-shaped guiding catheter is positioned in the coronary artery and then a dilatation catheter having a distensible balloon portion is advanced through the branches of the coronary artery until the balloon portion traverses or crosses a stenotic lesion. The balloon portion is then inflated with a fluid to compress the atherosclerosis in a direction generally perpendicular to the wall of the artery, thus dilating the lumen of the artery.
In the manufacture of balloon catheters and stent delivery systems, it is essential that the bonds between the catheter shaft and the balloon material be fluid tight and of sufficient strength to withstand the inflation fluid pressure. Typically, the balloon is mounted along the distal end region of the catheter body. In a multi-lumen balloon having a plurality of outer lumens disposed around a central lumen, the balloon outer lumens have tapered distal and proximal seal ends forming a fluted shaped balloon configuration. The balloon's proximal and distal seal ends are bonded to the catheter shaft via a proximal seal arrangement and a distal seal arrangement.
In some applications, including medical-related applications, two or more irregular shaped lumens or shafts must be bonded together so as to form a multi-lumen or multi-shaft assembly. Other applications may require that a material be bonded to a lumen or shaft that has an irregular shaped geometry.
There are several ways to bond a balloon to a catheter shaft, bond two or more lumens or shafts together into a multi-lumen or multi-shaft sub-assembly, or bond a material to an irregular shaped geometry.
One method to bond two or more lumens together into a multi-lumen sub-assembly or bond a material to an irregular shaped geometry is by using resistance heating of copper jaws. While the resistance jaws press the respective multi-lumens in the sub-assembly against each other the resistance jaws are heated until the lumens fuse. This method is particularly useful when bonding together shafts or lumens constructed of similar materials or of materials having similar material characteristics. However, this method provides unacceptable seals for when bonding components having multiple lumens, multiple shafts, or irregular geometries, for example, the non-circular geometry of the proximal and distal balloon seals of a multi-lumen balloon radiation centering catheter.
Another approach to bonding is to use adhesives or chemicals (i.e., solvent bonding). This approach is useful for multiple-lumen sub-assemblies being constructed of dissimilar materials. However, the adhesive layers add to the thickness of the area being bonded and increase its rigidity at the region of the bonds.
Yet another method for bonding is using a laser beam to target and heat up the region of interest until a seal is achieved. The laser seal configuration currently being used in most medical device applications has a helical or “rings” laser seal pattern. A laser beam is used to trace out a conventional “rings” pattern around the circumference of an area to be bonded such as where a balloon is being bonded to a catheter shaft. The helical laser seal pattern is achieved by directing a laser beam onto the balloon and catheter shaft while balloon and catheter shaft are rotated together about their longitudinal axis.
FIG. 1 shows a prior art helical or “rings” laser seal pattern 1, where a laser beam 20 traces out the conventional “rings” pattern 1 around a circumference 11 of an irregular-shaped (e.g., a non-circular) geometrical component such as a multi-lumen shaft bundle 10. The prior art helical laser seal pattern 1 shown in FIG. 1 is achieved by directing a laser beam 21 onto the irregular shaped multi-lumen shaft bundle 10 while the shaft bundle 10 is rotated about its longitudinal axis 12.
This prior art helical laser seal pattern has a number of disadvantages. For example, when laser sealing an multi-lumen, multi-shaft, or irregular geometry, the helical laser sealing pattern is unable to fully achieve a fluid tight seal. In other words, where the configuration to be sealed is not circular, oval or has another simple geometry, the helical sealing pattern may not seal all the areas along such geometries properly. For example, a multi-lumen balloon has an irregular shape and has grooves (or flutes) between the lumens for providing perfusion when in use. The helical laser sealing pattern may not form a fluid tight seal within these grooves.
Thus, what is desired is a method and apparatus for forming a seal (or bond) in multiple lumen, multiple shaft, and/or irregular geometry configurations.